some faces are darker with fine normals
You use a good few materials on certain objects and i first thought that might be the reason, removing them one by one brought me to the bad one.

Problem :The material, "platne white+color?", is the reason, more specifically the "Normal Map Node" which is set to "Tangent Space".

Solution: Changed to "Object Space", all was fine, see the video below.

Little extra:
Since i always check for wrong normals when there are issues, please bear with me, as i mentioned in the comments already. Your scene has 2 objects with a few of each that i would strongly advice to correct the normals from. May not have been an issue yet, but i's generally a very good idea to keep them blue(correct) to have no issues later with renders. Glass reflection and refraction as well as subdivision as well as maybe materials can all be affected.

I put a little video here to show you the bugger and the way to correct the normals, just in case you didn't know yet.

By fixing the material, all objects that used the same material got corrected as well. 
Also the material preview can give an indication that something might be wrong.